Choroidal vascularity profiles in diabetic macular oedema subtypes: a swept-source OCT angiography study

To characterise choroidal microvascular changes in diabetic macular oedema (DMO) subtypes using swept-source optical coherence tomography angiography (SS-OCTA).

This cross-sectional study analysed 182 eyes with centre-involved DMO from 141 patients (45 diffuse retinal thickening [DRT], 72 cystoid macular oedema [CMO], 65 serous retinal detachment [SRD]) and 40 age-matched healthy controls. Imaging was performed using the VG200 SS-OCTA system with a 1050 nm wavelength and 200,000 A-scans/second scan speed. Parameters including choroidal thickness (ChT), choroidal volume (CV), choroidal vascularity index (CVI), and choriocapillaris flow deficit percentage (CC FD%) were assessed in three macular annular regions (1-, 3-, and 6-mm diameter rings cantered on the fovea).

Compared to controls, all DMO subtypes exhibited choroidal microvascular dysfunction, including reduced CVI and increased ChT. Notably, SRD demonstrated the most severe flow deficits, with significantly larger CC FD% than both DRT (17.08 ± 10.83% vs 11.08 ± 7.38%, p = 0.002) and CMO (17.08 ± 10.83% vs 12.71 ± 8.16%, p = 0.014) in the 1-mm diameter ring. Similar differences were observed in the 3-mm diameter ring (SRD 12.66 ± 5.73% vs DRT 9.09 ± 5.00%, p = 0.002; SRD vs CMO 9.84 ± 5.11%, p = 0.007) and 6-mm diameter ring (SRD 9.87 ± 4.03% vs DRT 8.11 ± 4.40%, p = 0.003; SRD vs CMO 8.28 ± 4.07%, p = 0.026). No significant inter-subtype differences were found in CVI or ChT (p > 0.05).

Choroidal microvascular dysfunction is present in all DMO subtypes, with SRD exhibiting the most severe choriocapillaris flow deficits. These findings suggest potential subtype-specific pathophysiological associations.